1. Field of the Invention
The present invention relates to a color filter substrate preferably used in a liquid crystal display device, its manufacturing method, and a liquid crystal display device. More specifically, it relates to a color filter substrate having a laminated part which is laminated by a dry film laminating method and suitable for a spacer which specifies a thickness (cell gap) of a liquid crystal layer of a liquid crystal display device, its manufacturing method and a liquid crystal display device using that color filter substrate.
2. Description of the Related Art
Since the liquid crystal display device has merits, that is, it is small, thin, and light and its power consumption is low, it is widely used in various kinds of electronic devices. Especially, a liquid crystal display device which implements a color display by using a color filter (referred to as the “CF” hereinafter occasionally) substrate has excellent color reproducibility, so that it can be widely applied to an office automation (OA) device such as a personal computer, an audio visual (AV) device such as a television, a mobile phone and the like.
The liquid crystal display device has a structure in which a liquid crystal is sealed between a pair of substrates opposed to each other, and conventionally a thickness (cell gap) of the liquid crystal layer is retained constant by sphere or rod-shaped spacer (dispersed spacer) made of plastic beads or glass fiber which is dispersed on the substrate in many cases. However, it is difficult to arrange the dispersed spacer in a predetermined position on the substrate, and scattering of light caused by the spacer in the pixel (display area) or an alignment disturbance of a liquid crystal molecule in the vicinity of the spacer is generated, which causes the display quality to be lowered. In addition, there is room for improvement with respect to the following point. When the substrate to which the spacer is dispersed is pressed against the opposed substrate to be bonded, an opposed electrode or an alignment film is damaged by the dispersed spacer, so that the display defect is easily generated, and a contaminating material comes out of a damaged part, so that the display quality is easily lowered. In addition, it is necessary to provide a step of uniformly disperse the spacer on the substrate, and a step of maintaining grain size distribution at the time of dispersion with high precision, and it is difficult to provide a stable display quality.
Meanwhile, instead of the dispersed spacer, a method in which a resin film integrally formed with the substrate is used as a spacer for adjusting the cell gap comes into use, and especially, a method in which a photo spacer (referred to as the “PS” hereinafter occasionally) formed by patterning a photo resist film comes into use recently (refer to Japanese Unexamined Patent Publication No. 2001-221910 (P.1 and 7, FIG. 2), Japanese Unexamined Patent Publication No. Sho56-140324 (P. 1 and 6, FIG. 5(c)), Japanese Unexamined Patent Publication No. Hei4-93924 (P.1 and 6, FIGS. 2 and 3), Japanese Unexamined Patent Publication No. Hei5-196946 (P.1 and 3, FIG. 1), Japanese Unexamined Patent Publication No. 2000-147234 (P.1), Japanese Unexamined Patent Publication No. 2001-100221 (P.1, 13, and 16, FIGS. 1 and 6), Japanese Unexamined Patent Publication No. 2000-284111 (P.1 and 8, FIG. 1(b)) and Japanese Unexamined Patent Publication No. 2004-53654 (P. 2 and 30, FIG. 11(b)). Since the PS can be correctly arranged in a predetermined position on the substrate unlike the dispersed spacer, when the PS is arranged on a non-display area such as on a black matrix (referred to as the “BM” hereinafter occasionally) of the CF substrate or on a metal wiring of a thin film transistor (referred to as the “TFT” hereinafter occasionally) array substrate, the cell gap can be retained constant without lowering an aperture ratio. In addition, SP has a merit in which the display quality is not lowered due to the scattering of the light or the alignment disturbance of the liquid crystal molecule in the vicinity of the spacer like the dispersed spacer.
According to the Japanese Unexamined Patent Publication No. Sho56-140324, Japanese Unexamined Patent Publication No. Hei4-93924, Japanese Unexamined Patent Publication No. Hei5-196946, Japanese Unexamined Patent Publication No. 2000-147234, Japanese Unexamined Patent Publication No. 2001-100221, Japanese Unexamined Patent Publication No. 2000-284111 and Japanese Unexamined Patent Publication No. 2004-53654, a method in which a cell gap adjusting spacer comprising a plurality of laminated colored layers is used is proposed. The colored layer is formed of a photoresist in general, and the photo spacer having the laminated structure is referred to as a laminated photo spacer (laminated PS) in general. Since the laminated PS comprises the plurality of laminated colored layers, the spacer itself has light shielding property, so that even when it is arranged in the display area, the display quality is not lowered because of light leakage. In addition, when all of the layers constituting the laminated PS are formed of the same material as that used in the colored layer of the pixel region, its cost can be considerably lowered.
In addition, according to Japanese Unexamined Patent Publication No. 2001-100221, Japanese Unexamined Patent Publication No. 2000-284111 and Japanese Unexamined Patent Publication No. 2004-53654, as a method of forming the laminated PS, a dry film laminating (referred to as the “DEL” hereinafter occasionally) is proposed. According to the DFL method, a film (dry film) having a resin film provided on a supporting body is bonded to form the layer. When a resist resin film is used as the resin film, it is called a dry film resist (referred to as “DFR” hereinafter occasionally) method. According to the DFL method, a layer having a more uniform film thickness can be formed and the laminated PS having a more stable height can be formed as compared with a coating method using a liquid resist such as a spin coat method.
However, there is room for improvement in the case where the laminated PS is manufactured by the DFL method, when the dry film is bonded (laminated), air existing between the patterns formed already cannot escape and remains as a bubble, which causes the display defect in the liquid crystal display device. A degree of generation of the bubble is varied depending on a film thickness of the pattern (resist layer) formed already. Recently, since a color purity of the liquid crystal display device such as a liquid crystal television (TV) becomes increasingly high and a colored resist layer which constitutes the color filter layer becomes as thick as 1.5 to 2.5 μm, the air is more likely to be remained between the patterns at the time of laminating in the course of forming the laminated PS, so that the bubble is likely to be generated.